Dynamics of O2 photodesorption from metal clusters: A significant difference from bulk behaviour

Abstract

Photodesorption of O2 from size-selected Agn O2 - cluster anions with n = 2, 3, 4 and 8 was studied using time-resolved photoelectron spectroscopy (TR-PES). The spectra indicate that relaxations of photo-excited Agn O2 - clusters with n = even numbers accompany ultrafast direct O2 photodesorption. For the odd-numbered cluster Ag3 O2 -, in contrast, a long-lived excited state is observed, since O2 might be dissociatively chemisorbed, suppressing direct photodesorption of oxygen. Both, direct desorption and long-lived excited states, have not been observed from adsorbate covered metal surfaces, suggesting unique photochemical properties of such small clusters. © 2007 Elsevier B.V. All rights reserved.